Dye coupling between mouse Schwann cells.

Dye coupling and voltage-dependent ionic currents were evaluated simultaneously in mouse Schwann cells using patch pipettes containing Lucifer yellow. Dye coupling was examined in different types of cultured Schwann cells: cells not associated with axons, non-myelinating cells associated with axons, and myelinating cells. Myelinating and non-myelinating cells were also examined in freshly dissociated adult nerves. The incidence of dye coupling was higher in embryonic dorsal root ganglia (DRG) than in neonatal sciatic nerves. In both types of cultures the incidence of dye coupling decreased with time. In DRG cultures voltage-dependent K+ currents were observed in the Schwann cells, except in some of the myelinating cells, suggesting that K+ currents disappear as myelin formation progresses, and dye coupling was eliminated in myelinating cells. In freshly dissociated adult nerves, large myelinating Schwann cells lacked both K+ currents and dye coupling which were preserved in non-myelinating cells. Although the association between dye coupling and voltage-dependent K+ channels in non-myelinating cells is not clear, Schwann cells which had differentiated to engage in myelin formation lost both properties.